The Problems panel flags a configured tool path (app.tools) that no longer
points at a file — a real misconfig, echoing D-58's soft floor. A merely-
unfound optional tool isn't flagged (its use-time userError covers that).
Extracted to a pure supporterToolProblems(), flutter-tested (3 cases).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>